diatonic: A musical scale of eight notes spanning one octave, consisting of an ascending pattern of two whole-steps, a half-step, three whole-steps and another half-step. There are two types of diatonic scale in common use in western music: the diatonic major scale and the diatonic minor scale. Music which includes notes outside of the diatonic in which the piece is written is said to be chromatic.

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diatonic comma: After playing the Circle of Fifths, i.e., twelve ascending perfect fifths, followed by seven descending octaves, the pitch discrepancy between the ending note and the starting note is called the diatonic comma, or the comma of Pythagoras. This discrepancy amounts to a little over 1%, or about one-sixth of a half-step and gives rise to various temperaments in an attempt to distribute the error as harmoniously as possible. See scale construction, syntonic comma.

dichotic: Dichotic generally refers to headphone listening where each ear hears a different signal, as opposed to diotic, where both ears hear the same signal. See also monotic.

difference tone: A tone produced by combining two tones which are not part of a harmonic series, having a frequency difference of 20Hz or greater. Any slower than 20Hz, and the difference of the two notes will be perceived as a pulse, called beating. Also called a resultant tone. Also called a Tartini tone.

differential amplifier: Usually one of the signal input terminals of an amplifier is connected to the chassis of the amplifier, i.e., it is grounded. The amplifier is then sensitive to the voltage difference between the input terminal and ground. However, in a differential amplifier, neither input terminal is grounded. Instead, the amplifier is sensitive to the voltage difference between the two inputs. Used in professional mic preamps where a low-level signal has to go some distance, a differential amplifier cancels the hum induced by the proximity of the two input wires to a source of interference. In the UK, a differential amplifier is called an inverting amplifier. See differential input, common mode.

differential input: Signal input response to amplitude differences between two out-of- phase signals. Used in a balanced wiring system where the two wires carry signals that are identical, but 180° out-of-phase. The phase difference means that as a signal increases in voltage along one line, its mirror image on the other line decreases. This is useful because signals, such as hum and noise which have accumulated along a cable acting as an antenna, that are in phase are cancelled. See common mode, differential amplifier.

differential output: The output of an amplifier designed to provide two signals that are completely identical, but of opposite phase.

differentiator module: A highpass filter which can accentuate the higher-frequency harmonics and transients of a sound envelope. Compare with an integrator module.

diffraction: The bending of a sound wave around an obstacle and the reflection of a sound wave from an obstacle in its path are called diffraction. It is frequency dependent. Where the wavelength is short compared to the obstacle, reflection will occur as well as bending of the wave front. When the wavelength is long with respect to the obstacle, little reflection will occur and the bending will be more pronounced. See also refraction.

digital: In audio, the opposite of analog. The representation of audio or video as a series of encoded binary amplitude values, rather than as a continuous waveform.

Digital Acoustics Processor (DAP): A consumer audio device that attempts to simulate the acoustics of an auditorium or other room by adding suitable time delays and synthetic reverberation to recorded signals.

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digital audio: The application of digital technology to the recording, processing, and reproduction of music is somewhat loosely called digital audio, as opposed to analog.

Digital Audio Broadcasting (DAB): An alternative to AM and FM broadcasting with audio quality comparable to that of the CD, it does not suffer from fringe area fading or multipath distortion, and requires less radiated power than conventional broadcasting (1kW versus 50kW for AM and up to 100kW for FM.)

digital audio extraction: See grabbing.

Digital Audio Mastering System: See digital multitrack.

Digital Audio Recorder (DAR): Any type of audio recording system which records upon a digital medium, such as DAT or hard disk. DAT or DCC recorders, digital dubbers, digital multitracks, and hard-disk recording systems are all example of digital audio recorders. These recorders are an alternative to analog recorders, such as traditional cassette or reel-to- reel formats which do not convert the waveform to a digital representation prior to writing it to the recording medium.

digital black: In digital audio, a term which means complete silence. Digital black is calculated by taking the sample word length (e.g., 16, 20, or 24 bits) and multiplying this bit depth by 6dB, a number which represents the dynamic range represented by one bit. In a 16-bit system, for example, full code represents 96dB, the maximum amplitude that the system is capable of encoding without clipping. Digital black is at the opposite end of that dynamic range, or 96dB down from full code amplitude.

Digital Compact Cassette: A type of recording format announced by Philips in 1990, designed to compete with the R-DAT format. The system allows for the recording and playback of analog cassettes as well as DCCs on the same machine. Uses PASC (Precision Adaptive Subband Coding), derived from the MPEG-1, Layer 1 data reduction system to provide data compression (lossy) for the recording of digital audio on 18 ” wide magnetic tape at 17 8 ips. This format has not been widely adopted. Sometimes called DCAC for Digital Audio Compact Cassette. See also MiniDisc, DAT, and CD.

digital delay line (DDL): See delay line.

digital dubbers: Film industry term for a multitrack digital recorder, usually having eight tracks per unit, that use removable hard drives or magneto-optical drives as the recording medium. The term is partly a misnomer because previous film sound terminology had used dubber to describe a copying device as opposed to a recording device.

digitally controlled amplifier: See DCA.

digitally controlled oscillator: See DCO.

digitally controlled waveshaper (DCW): A DCW varies the timbre of synthesized sound by modifying the harmonic content of the tone produced by a DCO. See waveform.

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digital multitrack: A device for recording multiple channels of digital audio data at various sampling rates. Two formats have survived: the Sony/Studer DASH format and MDM machines of either ADAT or DTRS type. The first digital multitrack recorder was introduced in the late 1970s by 3M, a 32-track recorder called the Digital Audio Mastering System.

Digital Signal Processing (DSP): The manipulation and modification of signals in the digital domain, possibly after having undergone analog-to-digital conversion.

digital time delay: See delay.

digital-to-analog converter: Commonly abbreviated D/A, D/A converter or DAC. A device that changes the sample words put out by a digital audio device into analog fluctuations in voltage that can be sent to a mixer, amplifier, or speaker. All digital synthesizers, samplers, and effects devices have DACs at their outputs to create audio signals, as the transducers in loudspeakers are inherently analog devices.

Digital TeleVision (DTV): See DTV.

digital watermark: The solution for a piracy and duplication protection scheme developed jointly by Sony and Philips which writes copyright data encrypted within the CD/DVD etc. disc itself. This scheme would, for example, encode discs with a country code so that these discs would only play on players from the same country. This is presumably better than older forms of digital copy protection which tried various pilot tones or random number generators, failing ultimately because the results were either too audible or too easy to circumvent. In a digital watermark, the copyright data are stored as a modulation of the width of the injection-molded pits. Duplicating the watermark would require the same equipment as that which produced the disc stamper, the distribution of which is presumably tightly controlled. It is also possible to synchronize the modulation of the pit widths so that there is a visible pattern formed on the disc pit substrate itself, making an “analog” watermark (without the need for water, of course.) In addition to the watermark and country codes, identifiers for the mastering house and pressing plant, glass master number, ISRC catalog numbers, etc. can be stored.

The digital watermarking technology has been called Pit Signal Processing (PSP) which works by modulating the strength of the laser used to record the digital data onto the glass master. One by-product of the watermarking process is that the EFM used to encode audio data onto the CD master allows the pits to vary in length between 3-11 units. These slight errors in length, or “jitter” result in slight timing errors which can cause a smearing of the stereo image as well as an increase in HF noise. The more rigid requirements of pit length control in watermarking should result in a significant reduction of pressing-induced jitter, just generally improving the CD production process.

diminuendo: Synonym for decrescendo.

diminution: (1) The reduction of a major or perfect interval by one half-step to make a diminished interval. (2) The appearance of a musical idea in note durations which are shorter than those used for its first appearance. The opposite of augmentation. (3) A method ornamentation where notes of long duration are broken into a number of shorter notes, often at different pitches, e.g., a trill.

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DIN: Deutsche Institut für Normung. A German standards organization that proposed a set of connector configurations in the early 1960s. The standard MIDI connector is the 5-pin DIN where:

DIN sync: See pilot tone.

diode: A diode is a circuit element which will pass current in one direction only, from the anode (positive) to the cathode (negative). Used to make DC from AC.

diotic: Literally, “with two ears.” Diotic generally refers to headphone listening whereby the two ears hear the same signal, as opposed to monotic, where only one ear hears the signal. See also dichotic.

dip filter: A parametric equalizer with an extremely narrow Q, designed to remove noise in a small band such as that from a camera or light.

dipole: In loudspeaker design, a dipole radiator is a system which radiates forwards and rearwards with equal energy, but with opposite polarity. Examples of dipole radiators are electrostatic loudspeakers and planar speakers. Some cone-type speakers have dipole radiators. For a dipole radiator to have adequate low-frequency response, it must be very large to prevent the rear wave from canceling the front wave. Also, the dipole radiator must not be placed close to and parallel to a wall, working best when not near reflective surfaces.

direct box: See DI.

direct coupling: A connection between two devices that allows both DC and AC between them.

direct current (DC): Current in only one direction. DC always has the same direction, from the positive to the negative terminal. Compare with AC.

direct field: See reverberant field.